docs: def camel_to_snake(self, s):
          """Constructs nice dir name from class name, e.g. FooBar => foo_bar.
  
          :param s: The string which should be converted to snake_case.
          """
          return self._underscore_re2.sub(r'\1_\2', self._underscore_re1.sub(r'\1_\2', s)).lower()